(CBS News) At a news conference at the White House on Tuesday, President Obama lashed out at Mitt Romney and the other GOP presidential candidates for "the casualness with which some of these folks talk about war," saying their rhetoric on Iran reflects the fact that they "don't have a lot of responsibilities."

The president was asked about Romney's claim that "If Barack Obama gets re-elected, Iran will have a nuclear weapon." He responded first by pointing to his record, saying his administration has imposed "crippling sanctions" against Iran that have isolated the nation in an "unprecedented" way and significantly damaged its government economically.

He went on to say that while "we will not countenance Iran getting a nuclear weapon," he believes that "we have a window of opportunity where this can still be resolved diplomatically." He later said he does not believe that a decision by Israel on whether to attack must be made in the next two months, saying increasingly tough sanctions should have more time to work.

"Because sanctions are starting to have significant effect inside of Iran -- and that's not just my assessment, that's, I think, a uniform assessment -- because the sanctions are going to be even tougher in the coming months, because they're now starting to affect their oil industry, their central bank, and because we're now seeing noises about them returning to the negotiating table, that it is deeply in everybody's interests, the United States, Israel and the world's, to see if this can be resolved in a peaceful fashion," he said.

The president also criticized the rhetoric coming from the GOP presidential candidates.

"Now, what's said on the campaign trail -- you know, those folks don't have a lot of responsibilities. They're not commander in chief," he said. "And when I see the casualness with which some of these folks talk about war, I'm reminded of the costs involved in war; I'm reminded of the decision that I have to make, in terms of sending our young men and women into battle, and the impacts that has on their lives, the impact it has on our national security, the impact it has on our economy."

In a speech to the American Israel Public Affairs Committee (AIPAC) Tuesday, Romney attacked Mr. Obama's approach to the Middle East, saying "hope is not a foreign policy." In an op-ed Monday, Romney laid out how he would deal with Iran and criticized Mr. Obama's policies and tone - despite the fact that his approach is essentially identical to that of the president.

"And, you know, when I see some of these folks who have a lot of bluster and a lot of big talk but when you actually ask them specifically what they would do, it turns out they repeat the things that we've been doing over the last three years, it indicates to me that that's more about politics than actually trying to solve a difficult problem," he said.

The president also said that "If some of these folks think that it's time to launch a war, they should say so."

"And they should explain to the American people exactly why they would do that and what the consequences would be," he said. "Everything else is just talk."

Romney is just one of the GOP presidential candidates who have criticized Mr. Obama over his policy on Iran -- and, by extension, Israel. Newt Gingrich has said that America is "being played for fools"; Rick Santorum told AIPAC that "If Iran doesn't get rid of nuclear facilities, we will tear down them ourselves." Ron Paul has broken with his GOP colleagues on the issue, telling CNN Tuesday that "what the other Republicans are saying is very reckless" and reminds him of the run-up to the Iraq war.

Mr. Obama said Tuesday that "those who are suggesting or proposing or beating the drums of war should explain clearly to the American people what the costs and benefits should be," adding, "I'm not one of those people."

"Because what I've said is, is that we have a window through which we can resolve this issue peacefully," said Mr. Obama. "We have put forward an international framework that is applying unprecedented pressure. The Iranians just stated that they are willing to return to the negotiating table. And we've got the opportunity, even as we maintain that pressure, to see how it plays out."

He added that "this notion that somehow we have a choice to make in the next week or two weeks or month or two months is not borne out by the facts."

Mr. Obama's comments echo Massachusetts Sen. John Kerry's criticism of Romney's claim that Iran will get a nuclear weapon if the president is reelected. Kerry told the New York Times that "to be making a blanket statement that if he's president they'll have one, and if Romney's president they won't have one, is the most craven political thing to say." He added: "To make up differences is to play in Iranian hands."

"It was not a military doctrine that we were laying out for any particular military action," he responded.

The president said that the comment, taken by many as a sign that the United States could support an Israeli military strike on Iran, was "a restatement of our consistent position that the security of Israel is something I deeply care about." He added that "Israel is a sovereign nation that has to make its own decisions about how best to preserve its security."